Optics 2

Eyes. Photo: Manuel Meurisse, 2017-11-17, Tasmania, Australia

This is the second of nine posts about optics.

Optical devices interact with eyes and a brain, so that the content being observed can be interpreted relevantly. Cameras, binoculars, microscopes and other analogue optical devices, can subject eyes to excessive strains. For example, looking even indirectly at the sun during a solar eclipse using inappropriate aids, invites permanent damage to the eyes. Optics mediated through a digital screen are less problematic, because the screens come equipped with limits on their optical capabilities. That said, screen brightness settings can be excessive, either too low or too high for the eyes using them. Personally, I routinely set my digital devices to 20% of the maximum allowable. I also select black backgrounds. I have often wondered if this light sensitivity is related to my blue eyes. Other people may have completely different needs.

Vision changes

As a person ages, it is common for them to find that they can’t see as well as they once did. That’s a normal development. They will probably need glasses or contacts. If a person already uses them, they may need a stronger prescription. Some people may choose to have Laser-Assisted in Situ Keratomileusis (LASIK), commonly referred to as laser eye surgery or laser vision correction. There are mixed opinions (and little scientific evidence, as far as I can find) about the suitability of LASIK.

Presbyopia is the name given to the situation where a person loses the ability, despite good distance vision, to see close objects and small print clearly. After age 40 or so, people may have to hold a book or other reading material farther away from their eyes to make it easier to read. Many complain that their arms are too short. Reading glasses, contact lenses, and other procedures can be used to restore good reading vision.

Other, more serious conditions also happen as people age. Eye diseases like macular degeneration, glaucoma and cataracts, can cause vision problems. Symptoms vary a lot among these disorders.

Colour blindness

When a person cannot see certain colors, or can’t tell the difference between them (usually reds and greens), that person may be colour blind. It happens when the cone cells, used to distinguish colour, are absent or fail to work. When it is most severe, a person can only see in shades of gray, but this is rare. Most people who have colour blindness are born with it, but one can get it later in life from certain drugs and diseases. Men are much more likely to be born with it than women.

Paddy, the father of my wife, Trish, had red-green colour blindness, so I have been concerned about people inheriting this. There are free online colour blindness tests. I have taken one here, and found that I have normal vision. There’s no treatment if a person is born colour blind, but special contacts and glasses can help some people tell the difference between certain colors.

My son, Alasdair, has also taken numerous colorblindness tests with no indication of colour blindness. In middle school he created such a test and was able to diagnose one of his peers as colour blind. Until then, this child was unaware of his condition. My daughter, Shelagh, informs me that it’s common practice in web development to check designs to ensure they pass colour blindness tests.


Eyes can be overused. They get tired and need to rest. Give eyes that feel strained time off.

Red Eye

The surface of eyes is covered in blood vessels that expand when they’re irritated or infected. That gives eyes a red look. It can be caused by eyestrain, a lack of sleep, allergies, or something more serious: an injury, conjunctivitis (pinkeye) or sun damage. Over-the-counter eye drops can sometimes help, along with rest.


Amblyopia = Lazy eye is a situation where one eye does not develop properly. Vision is weaker in that eye, and it tends to move “lazily” around while the other eye stays put. It’s found in infants, children, and adults, but rarely affects both eyes. Treatment needs to be sought immediately for infants and children.

Lifelong vision problems can be avoided if this is detected and treated during early childhood. Treatment includes corrective glasses or contact lenses and using a patch or other strategies to make a child use the lazy eye.


If both eyes aren’t lined up with each other when one is looking at something, the problem could be strabismus = crossed eyes = walleye. This problem is often corrected using vision therapy, where weak eye muscles are strengthened. At other times, surgery is necessary.


With nystagmus, an eye moves/ jiggles all the time on its own. Vision therapy is one treatment option. Surgery is another.


Uveitis is the name for a group of diseases that cause inflammation of the uvea, the middle layer of the eye that contains most of the blood vessels. These diseases can destroy eye tissue, and even cause eye loss. People with immune system conditions like AIDS, rheumatoid arthritis, or ulcerative colitis may be more susceptible to uveitis. Common ymptoms include: blurred vision; eye pain; eye redness; and, light sensitivity. Treatments vary, dependent on the type of disease.


These are tiny spots or specks that float across a field of vision. Most people notice them in well-lit rooms or outdoors on a bright day.

Floaters are usually normal, but they sometimes can be a sign of a more serious eye problem, like retinal detachment. That’s when the retina at the back of an eye separates from the layer underneath. When this happens, a person might also see light flashes along with the floaters or a dark shadow come across the edge of their sight.

If a person notices a sudden change in the type or number of spots or flashes they see or a new dark “curtain” in appears in their peripheral vision, it is advisable to see an eye doctor as soon as possible.

Dry Eyes

This happens when eyes can’t make enough good-quality tears. A person might feel like something is in their eye or that it is burning. Rarely, in severe cases, extreme dryness can lead to some loss of vision. Some treatments include:

  • Using a humidifier
  • Special eye drops that work like real tears
  • Plugs in tear ducts to lessen drainage
  • Lipiflow, a procedure that uses heat and pressure to treat dry eyes
  • Testosterone eyelid cream
  • Nutritional supplements with fish oil and omega-3

If a dry eye problem is chronic, it could indicate dry eye disease. A doctor could prescribe medicated drops like cyclosporine (CequaRestasis), lifitegrast (Xiidra), or Tyrvaya nose spray to stimulate tear production.

Excess Tearing

It has nothing to do with feelings. A person might be sensitive to light, wind, or temperature changes. Try to protect eyes by shielding them or wearing sunglasses (go for wraparound frames — they block more wind than other types).

Tearing may also signal a more serious problem, like an eye infection or a blocked tear duct. An eye doctor can treat or correct both of these conditions.


These are cloudy areas that develop in the eye lens.

A healthy lens is clear like a camera’s. Light passes through it to the retina — the back of the eye where images are processed. With a cataract, light can’t get through as easily. The result: A person can’t see as well and may notice glare or a halo around lights at night.

Cataracts often form slowly. They don’t cause symptoms like pain, redness, or tearing in the eye.

Some stay small and don’t affect sight. If they do progress and affect vision, surgery almost always works to bring it back.


An eye is like a tire: Some pressure inside it is normal and safe. But if levels are too high it can damage the optic nerve. Glaucoma is the name for a group of diseases that cause this condition.

A common form is primary open angle glaucoma. Most people who have it don’t have early symptoms or pain. This is often part of a regular eye examination.

Glaucoma can be caused by:

  • An injury to the eye
  • Blocked blood vessels
  • Inflammatory disorders of the eye

Treatment includes prescription eye drops or surgery.

Retinal Disorders

As previously noted, the retina is a thin lining on the back of the eye that is made up of cells that collect images and pass them on to the brain. Retinal disorders can damage retinal cells and block this transfer. There are different types:

  • Age-related macular degeneration refers to a breakdown of a small portion of the retina called the macula.
  • Diabetic retinopathy is damage to the blood vessels in the retina caused by diabetes.
  • Retinal detachment happens when the retina separates from the layer underneath.

It’s important to get an early diagnosis and have these conditions treated.

Conjunctivities (Pinkeye)

In this condition, tissue that lines the back of the eyelids covering the sclera gets inflamed. It can cause redness, itching, burning, tearing, discharge, or a feeling that something is in one’s eye.

People of all ages can get it. Causes include infection, exposure to chemicals and irritants, or allergies.

Wash hands often to lower chance of getting it.

Corneal Diseases

The cornea is the clear, dome-shaped “window” at the front of an eye. It helps to focus the light that comes in. Disease, infection, injury, and exposure to toxins can damage it. Signs include:

  • Red eyes
  • Watery eyes
  • Pain
  • Reduced vision, or a halo effect

The main treatment methods include:

  • A new eyeglasses or contacts prescription
  • Medicated eye drops
  • Surgery

Eyelid problems

Eyelids are important for: protecting eye, spreading tears over its surface, and limiting the amount of light that can enter.

Pain, itching, tearing, and sensitivity to light are common symptoms of eyelid problems. One might also have blinking spasms or inflamed outer edges near eyelashes.

Treatment could include proper cleaning, medication, or surgery.

Some vision changes can be dangerous and need immediate medical care. Anytime a person has a sudden loss of vision, or vision becomes blurry seek medical advice.

Contact Lenses

I have never used, nor wanted to use, contact lenses. However, I understand that cleanliness is essential for their use. Users are advised to follow the care guidelines that came with their prescription. There is a need for users to

  • Wash their hands before touching contact lenses.
  • Never use saliva to wet them.
  • Ensure the lenses fit properly, to avoid scratches.
  • Use eye drops that say they’re safe for contact lenses.
  • Never use homemade saline solutions. Even though some lenses are FDA-approved for sleeping in them, doing so raises the risk of a serious infection.

If a person does everything right and still have problems with contacts, see an eye doctor. The person might have allergies or dry eyes. Once the problem is known, a person can decide the best course of action, which could include opting to use glasses.

Night Blindness

Night blindness is more of a symptom, than a problem. Nearsightedness, cataracts, keratoconus, or a vitamin A deficiency can all provoke these symptoms, that can be treated. At other times it is a symptom of a degenerative retinal disease that usually can’t be treated.

Note: This post started as my personal checklist about eye health issues. However, it has been augmented with additional problems, that people may encounter. The content has been accumulated over a number of years from unremembered sources, including Wikipedia. Some of these issues will need medical attention, while others are more trivial. The challenge is distinguishing between the two. So if what appears to be a trivial complaint persists, it could be appropriate to seek medical attention, to make sure it is not a more serious problem.

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